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Heathkit W5M rebuild problem

M

MAShia13

New Member
Hi all,

I have just completed a complete rebuild of a pair of W5M amps that I purchased 10 years ago. (the 16458 OPT). I did a complete gut job, all new ceramic gold plated sockets, the Sheldon Stokes cap board, decent components, matched resistors etc. The amps were then rebuilt in parallel. Everything seem to work just fine, the output tubes balanced easily, pluged them in to a preamp and speakers everything was perfect except, one amplifier has twice the output of the other. I though I was a decent trouble shooter, but so far I cannot find any substantial differences, I have swapped all the tubes, measured the voltages (heathkit specs in manual), traced a signal with my scope, etc. The only thing I can figure is that the output transformers are different (although they seem to be electrically similar as measured with an ohm meter) or that there is something in the feedback pathway. There is no hum, they both sound good, except one is more powerful. Any ideas?

Thanks

Michael
 
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If you have eliminated the source, cables, hookups, speakers and is only left with the amp then there is something most likely drawing your signal down. So i would look for either a mistake in your assembly of the bad amp. You need to check super carefully to make certain you did not put a component on for example, pin 6 instead of pin 7 or vice versa. The other thing is there might be a small bit of wire or solder glob that has eked out and has made contact with ground. Everyone who has done rebuilding of a tube amp has had this problem so it just takes patience and very careful checking under a bright light to make sure everything is correctly connected with no shorts to ground.
 
MAShia13 said:
Hi all,

I have just completed a complete rebuild of a pair of W5M amps that I purchased 10 years ago. (the 16458 OPT). I did a complete gut job, all new ceramic gold plated sockets, the Sheldon Stokes cap board, decent components, matched resistors etc. The amps were then rebuilt in parallel. Everything seem to work just fine, the output tubes balanced easily, pluged them in to a preamp and speakers everything was perfect except, one amplifier has twice the output of the other. I though I was a decent trouble shooter, but so far I cannot find any substantial differences, I have swapped all the tubes, measured the voltages (heathkit specs in manual), traced a signal with my scope, etc. The only thing I can figure is that the output transformers are different (although they seem to be electrically similar as measured with an ohm meter) or that there is something in the feedback pathway. There is no hum, they both sound good, except one is more powerful. Any ideas?

Thanks

Michael
Click to expand...
Have a peek at the louder amp if something is wrong with the feedback circuitry.
 
MAShia13 said:
Hi all,

I have just completed a complete rebuild of a pair of W5M amps that I purchased 10 years ago. (the 16458 OPT). I did a complete gut job, all new ceramic gold plated sockets, the Sheldon Stokes cap board, decent components, matched resistors etc. The amps were then rebuilt in parallel. Everything seem to work just fine, the output tubes balanced easily, pluged them in to a preamp and speakers everything was perfect except, one amplifier has twice the output of the other. I though I was a decent trouble shooter, but so far I cannot find any substantial differences, I have swapped all the tubes, measured the voltages (heathkit specs in manual), traced a signal with my scope, etc. The only thing I can figure is that the output transformers are different (although they seem to be electrically similar as measured with an ohm meter) or that there is something in the feedback pathway. There is no hum, they both sound good, except one is more powerful. Any ideas?

Thanks

Michael
Click to expand...

My first thought is that the feedback is hooked up wrong on the louder amp. Check that connection and make sure it's correct.
 
A little voice from a time when I rebuilt 4 of those is whispering about the RCA replacement jacks.
I seem to remember "something" about the mounting/grounding on those.
Recheck that work.
 
With a 6V heater TX, feed the 16R secondary. It is best to use a variac so as to deliver just a few volts. measure the voltage at the pin 3 of the output tubes. Amps turned off and B+ decayed to zero or effectively that. Then repeat for the 8 and 4R taps.
cheers,
Douglas
 
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